In February 2024, a research team at Lehigh University led by John Fox, Associate Professor in the Department of Civil and Environmental Engineering, learned that it had been awarded a $2 million, three-year grant from the Department of Energy’s Industrial Efficiency and Decarbonization Office (IEDO) for its proposal, “Decarbonizing Concrete: Low-Temperature Calcined Clays as an Alternative Concrete Binder, Achieving Durability with Clay Beneficiation.” The team also consists of Clay Naito, Professor in the Department of Civil and Environmental Engineering; Paolo Bocchini, Professor in the Department of Civil and Environmental Engineering; and Carlos Romero, Director and Principal Research Scientist of the Energy Research Center.
IEDO states that the purpose of the award is to “drive improvements in energy, materials, and production efficiency, and to accelerate decarbonization across the industrial sector.” Fox’s project has the potential to speed up the process of developing low-carbon or net-zero technology for commercialization in the concrete industry. The Lehigh team will focus on the processing and testing of calcined clay to develop a material that has properties similar to those of ordinary Portland cement, but without the greenhouse gas (GHG) emissions typical of its production.
The research project also involves Bethlehem’s Buzzi Unicem USA, a leading cement manufacturing company which has previously collaborated with Lehigh researchers on other projects. Shamim Pakzad, Professor and Chair of the Civil and Environmental Engineering Department, is optimistic about the partnership between industry and academic research. He says, “This grant shows the opportunities of synergy between academia and industry, and how it could lead into high level and impactful research. I am particularly excited about the expansion of the research portfolio of CEE departments into this area of greener cement, which opens many opportunities for future research and implementation in industry.”
The cement industry presents a huge opportunity for lower-emission innovation, because its traditional production methods can be environmentally harmful and because it is used in so many ways, particularly in construction. Concrete is generally made by adding water to cementitious materials to form a binder which is mixed with sand and stone aggregate. The most popular modern binder relies on ordinary Portland Cement (OPC), which is produced by heating limestone to extreme temperatures (over 2,500 degrees F). OPC contributes to carbon dioxide emissions in two ways during production: first, the heating process uses fossil fuels, which form carbon dioxide during combustion; and second, limestone undergoes a chemical transformation called calcination that directly releases carbon dioxide during heating. Due to the significant volume of cement used and carbon intensity of production, ordinary Portland Cement production is responsible for 4% to 8% of the world’s carbon dioxide. Because of this tremendous scale, finding a replacement for the OPC is crucial to creating a net-zero economy.
Fox and his team will work with a possible replacement, low-grade calcined clay. This lower-cost and more available limestone-free clay does not directly emit carbon dioxide during heating and can be calcined at lower temperatures than limestone. A variety of low-grade clays are available within the U.S. for the research effort. Part of the team’s testing will involve cleaning, milling, and appraising the properties of these different clays, as well as measuring the carbon footprint of each.
Buzzi will supply several varieties of low-grade calcined clay. The team at Lehigh will combine these clays in various mixes, create mortar cubes, and test their performance in multiple tests for compressive strength and for mechanical and durability qualities, such as freeze-thaw cycle, abrasion resistance, and chloride migration.
The project’s overall goal is to produce an economically viable calcined clay that, when mixed, produces half the CO2 of traditional mixes. Considering that concrete is the second-most used material in the world (after water), this would be a big step toward the reduction of carbon dioxide emissions.